I am an atheist but of course that is only a matter of faith in the same way that that those who believe in God have faith.

You cannot prove nor disprove the existence of God.

As soon as you accept that God could be responsible for creating the singularity that initiated the "Big Bang" then you have to accept that God could have spoken to man through the various religious texts which are the basis of the various religious groups.  After all in comparison to the "power" required to create the start of the universe this would be just a small matter for such a God.

Those that won't accept that God could be responsible for everything in existence and the way it has been formed are just as closed in their opinions as those who won't accept that it could be possible that there is no God.

The bottom line is that it it is a matter of faith one way or the other, neither can be proved, both faiths have equal standing and belief in one or the other should be no excuse for insulting or being derogatory about those with opposite beliefs.